1. Field of the Invention
The present invention relates to a method of processing a graphic data using a CAD system in order to display a graphic image combining graphic elements such as curvilinear lines, segments, and circles, a processing apparatus employing the method, and a computer program product for realizing the processing apparatus with use of a general-purpose computer. Particularly, the present invention relates to a processing method, a processing apparatus, and a computer program product for determining the identity of two graphics.
2. Description of the Related Art
CAD (Computer Aided Design) systems have been marketed for processing graphic data to display a graphic image combining graphic elements such as curvilinear lines (free curves), segments, and circles.
As such graphic data are processed in different CAD systems, they are varied but not uniform in the data structure or the file format for representation. Therefore, the graphic data has different contents depending on the file format, even they are displaying same graphic images.
For standardization and digitalization of a variety of documents including graphic data to promote the data exchange over the public networks, the Ministry of Land, Infrastructure, and Transport in Japan adopted as a standard file format for official graphic documents the SXF format conforming to the ISO standard STEP/AP202 which was highly improved in the standardization and the neutralization and started from October in 2002.
However, every graphic data file specified as the SXF format is highly bulky in the data size and may hardly be practical as is heavy for use as the data file in a CAD system.
It is assumed that as a contractor wants to build a facility, it assigns a designer to design, a constructor to construct, and a maintainer to maintain the facility. A graphic data for the facility is created by the designer at a format for a CAD system of type A and then converted into an SXF format which is delivered to the contractor.
The graphic data of the SXF format is then supplied from the contractor to the constructor. The constructor then does various processing after converting the graphic data of the SXF format into a format for a CAD system of type B for the construction.
Also, the graphic data of the SXF format is supplied for the contactor to the maintainer. The maintainer then does various processing after converting the graphic data of the SXF into a format for a CAD system of type C for the maintenance.
It may particularly be desired to ensure the identity of graphic data at the discrete formats between the contractor, the designer, the constructor, and the maintainer or determine whether or not any illegal access or falsification is contained.
In addition, what graphics displayed by the graphic data are identical with each other means that the graphic elements such as curvilinear lines, segments, and circles constituting the graphic data are identical to those, and the same graphics can be outputted.
The conventional comparison between the graphic data is executed in the same CAD system using same file format. In practice, the graphic element data displaying the graphic elements constituting the graphic data are compared one by one.
FIG. 7 is an explanatory view schematically illustrating the graphic element data used for comparing the graphic data in a conventional manner.
As shown in FIG. 7, each of the graphic element data is represented as a record of the attribute of the graphic element such as graphic type, color, line type, and line width and a location coordinate indicating the position to be located and configuration represented by coordinates.
The graphic type of the graphic element is an information for representing graphic type such as curvilinear line, segment, and circle.
The color of the graphic element is an information for representing a color of the graphic element such as red, yellow, and green.
The line type of the graphic element is an information for representing the type of a line of the graphic element such as solid line, broken line, or one-dot chain line.
The line width of the graphic element is an information for representing the width of a line forming the graphic element such as 0.6, 0.8, and 1.0.
The location coordinate of the graphic element is an information for indicating the position to be located and configuration of the graphic element. When the graphic type of the graphic element is a segment, its two ends are represented by the coordinate. When the graphic type of the graphic element is a circle, its center is represented by the coordinate in combination with a radius. When the graphic type of the graphic element is a curvilinear line, its tracing points are represented by the coordinate.
When the graphic type of the graphic element is a character, its start point and the character train and the like become the location coordinate.
As the graphic element data displaying the graphic elements constituting the graphic data are compared one by one, the identity of the graphic data can be determined.
It may be essential to ensure the identity of graphic data not only for determining whether or not any illegal access mentioned above is done but also for judging the conversion of a file format from one to another with no error.
A system for determining the identity of graphic data by comparing the attributes (graphic parameters) of the graphic data (CAD data) is disclosed in, for example, Japanese Application Laid-open No. 6-83913(1994).
In the conventional method, however, it is not supposed that the graphic data between different formats such as between the format for CAD system of type A and the SXF format.
Also, since the graphic elements are compared one by one in each of the attribute of graphic type, color, line type, line width, and coordinates, the processing load such as processing time is considerably large.
Particularly, curvilinear line as the free curve needs a number of coordinates points for the comparison. In addition, the coordinates include decimals or fractional numbers other than integers. As a result, they will be processed only with an increase in the processing load.
As all the graphic elements are compared, the overall processing load will further be increased.